Device for controllably altering the curvature of the cornea

ABSTRACT

The present invention is a device that improves visual acuity by reshaping the cornea, by subjectively altering the corneal curvature in the optic zone by increasing the mechanical stiffness of the cornea outside (and/or slightly inside) the optic zone. One or more of the corneal battens are inserted into the cornea, after selectively distorting the natural corneal shape. Once inserted the stiffness of the corneal batten prevents the cornea from returning to its original curvature.

FIELD OF THE INVENTION

[0001] The present invention relates to an apparatus and method ofreshaping the cornea, and more particularly to a semi-rigid memberadapted for insertion into the cornea of the eye to correct refractiveerrors.

BACKGROUND OF THE INVENTION

[0002] Approximately eighty percent of the refractive power of the eyeis at the cornea. As shown in FIGS. 1 and 2, the cornea is comprised ofseveral layers. Starting on the outside (anterior) surface, there is theepithelium. This layer is ca. 6 cells thick. Beneath the epithelium isthe Bowman's layer, a thin, primarily acellular collagen layer. The bulkof the mechanical strength of the cornea comes from the stroma whichlies beneath the Bowman's layer. The stroma comprises the bulk of thecornea and is made of layers of oriented collagen fibers. Theorientation of the fibers is very precise and the axial directionchanges with each layer. On the interior (posterior) surface of thecornea are the Descemet's membrane and then the one cell thickendothelium.

[0003] The schematic eye assumes an orb of 13 mm radius on which isfound a clear corneal membrane of 7.7 mm anterior radius and 6.8 mmposterior radius and a 0.55 mm center thickness (CT) in the optical zone(OZ). If the orb of the eye is truncated or elongated and/or if theradii or CT of the cornea are not of schematic dimensions, then the eyewill be myopic or hyperopic. Depending on the severity of deviation fromschematic dimensions, the patient will need spherical correction in theform of surgery, contact lenses, and/or spectacles to achieve maximumvisual acuity.

[0004] In spherical corrections, myopic patients need to reduce thepower of the cornea. This is achieved in surgery by enlarging the radiusor “flattening” the curve. When treated with lenses (contact orspectacle), myopic patients have “minus” power lenses. Hyperopicpatients have corneas that are too flat. Surgical treatments are aimedat decreasing the radius of curvature or “steepening” the curve. Iftreated with lenses, hyperopic patients wear “plus” power lenses.

[0005] Likewise, if the anterior (or posterior) radius of the corneal isnot uniform as one scans around the pupillary axis (or the axis ofsymmetry which runs through the center of the OZ), the cornea is said topossess astigmatism. Astigmatism can also be corrected through surgeryor through the use of “toric” lenses (either contact or spectacle).Regular astigmatism can be broken down into lens system in which acylindrical lens is imposed on a spherical lens. In irregularastigmatism, the astigmatic portion of the lens system is somethingother than cylindrical.

[0006] A variety of means have been proposed to reshape the cornea tobring about spherical and/or stigmatic correction. These methods fallinto four major classes: optical elements, stromal removal, stromalremodeling, and non-optical implants.

[0007] Optical element methods involve placing another material in theoptical path, as shown in U.S. Pat. Nos.: 4,799,931; 4,851,003,5,108,428, and 5,201,762. A class of the optical elements can be thoughtof as a hydrogel contact lens placed inside the cornea. In someinstances, the optical element relies on a higher index of refractionfor the implanted material in order to effect greater optical correctionwith less material. Others rely merely on the bulk of the implantedmaterial altering the curvature sufficiently to achieve the desiredcorrection. Either way, it is important that the material be opticallytransparent, capable of diffusing water, gasses, salts, and othernutrients, and non-toxic/bio-acceptable.

[0008] Stromal removal is one of the earliest methods employed toreshape the cornea. One such method involves freezing the cornea andremoving a thick layer of the optic zone. This so-called “button” wasplaced on a lathe and stromal material was cut off using very sharplathe tools. Other methods have proposed removing epithelial, Bowman's,and stromal tissue in situ, U.S. Pat. No. 4,834,748.

[0009] In recent years, stromal ablation has been used. Most often thisis done with lasers, e.g., U.S. Pat. No. 4,988,348, but has also beenproposed with radio-frequency electromagnetic radiation, e.g., U.S. Pat.No. 4,907,586. One such procedure, generally referred to asphoto-refractive-keratotomy (PRK), involves the removal of theepithelial layer (with or without removing Bowman's layer) prior toablating the stroma, as shown in U.S. Pat. Nos.: 5,269,795; 5,632,757;and 5,649,943. The epithelium takes several days to recover the entireoptic zone.

[0010] Another procedure, referred to as LASIK, involves the cuttingback as a thin flap the epithelial layer, Bowman's layer, and a thinlayer of stroma prior to ablation of the stromal bed. The flap includesthe entire optic zone. Using this flap speeds recovery since theepithelial cells do not need to regenerate. Moreover, the Bowman's layeris left largely intact.

[0011] A well-studied method of stromal remodeling is radial keratotomy(RK). In an RK procedure, 1 to 16 radial incisions (preferably fewerthan 5) are made into the anterior surface of the cornea. The incisionsrun from the periphery (or sometimes inside) of the OZ to the limbus(the junction of the cornea with the sclera). The cuts can be as deep as90% (or more) of the stromal thickness. The cuts weaken the cornea andpermit it to sag (take on a smaller radius of curvature) outside of theOZ. This causes flattening inside the OZ. As the stromal and epithelialcells remodel the wounded area (normal wound healing), the corneacontinues to change shape. This ongoing remodeling as well as the lackof a precise correlation between cut geometry/placement and finalcorneal shape are two major drawbacks of the RK procedure itself. Otherdrawbacks include corneal perforation and night (glare) blindness due tolight scattering off of that portion of the incision that is inside theOZ.

[0012] Another method of stromal remodeling involves thermaldenaturation of the proteins in the stroma. Collagen is the primary formof protein in the stroma and heating can change its morphology. Avariety of methods have been proposed to effect denaturation of thestromal collagen, including, ultrasonic energy, U.S. Pat. No. 3,776,230,radio-frequency electromagnetic energy, U.S. Pat. No. 4,381,007, andlaser, U.S. Pat. No. 5,374,265. Stromal remodeling can be performed withor without the application of a hard contact lens or other surface tomold the cornea while the stromal cells remodel the damaged collagen,U.S. Pat. Nos. 3,776,230 and 3,831,604.

[0013] A third method of stromal remodeling involves using drugs, U.S.Pat. No. 3,760,807, or enzymes, U.S. Pat. No. 5,270,051, to soften thecorneal material. A rigid contact lens or similar mold surface is heldagainst the corneal until the corneal material returns to its originalmechanical strength. The mold or lens is removed and the corneal retainsthis new shape. It has even been proposed that this remodeling can beeffected simply by holding a mold of proper shape against the cornea fora time sufficient for the cornea to remodel itself in response to theforces imposed by the mold, U.S. Pat. No. 5,695,509.

[0014] Another method of reshaping the cornea is with non-opticalcorneal inserts. A number of intrastromal inserts have been proposedwhich are to be placed just outside of the optic zone, including, U.S.Pat. Nos.: 5,733,334, 5,792,161, 5,824,086, 5,843,105, 5,855,604,5,876,439, and 5,944,752. One groups of inserts is a split ring. Onceimplanted, the split ring is expanded or contracted to an extent thatprovides the amount of reshaping that is desired in the optic zone. Thering is then fixed in that configuration.

[0015] Another group of implants is a hollow ring. The thickness of theimplanted ring is adjusted by adding or removing material from theinternal void in the ring. This change in thickness alters the shape ofthe cornea in the optic zone.

[0016] A third group of implants is comprised of two, nearlysemicircular, ring segments. One segment is implanted on each side ofthe optic zone. The thickness of the implant determines the extent towhich the curvature of the optic zone is altered.

[0017] Notwithstanding the foregoing, there remains a need for animproved method of reshaping the cornea, which can produce substantiallypermanent results in a short time period.

BRIEF SUMMARY OF THE INVENTION

[0018] The present invention is in the class of processes and devicesthat improve visual acuity by reshaping the cornea. Whereas previousprocesses and devices have been disclosed which reshaped the corneal byuse of optical elements, removing stromal (and other) tissue, thickeningthe cornea outside the optical zone, or by weakening or otherwisedamaging the stromal tissue, the present invention subjectively altersthe corneal curvature in the optic zone by increasing the mechanicalstiffness of the cornea outside (and/or slightly inside) the optic zone.

[0019] The present invention, referred to herein as a corneal batten,comprises minute fibers made from materials with a Young's modulusgreater than the Young's modulus of the corneal stroma. One or more ofthe corneal battens are inserted into the cornea, after selectivelydistorting the natural corneal shape. Once inserted the stiffness of thecorneal batten prevents the cornea from returning to its originalcurvature.

[0020] The corneal batten is surgically implanted into the cornealstroma. The curvature of cornea is controllably altered by thefollowing: selection of the position of placement of the cornealbattens; varying the number of corneal battens implanted; varying thedimensions of implanted corneal battens; and by flattening or overcurving the corneal during placement of the corneal battens. Theinserted corneal battens will act to alter the original curvature of thecornea and bring about improved visual acuity.

[0021] The radius of curvature of the optic zone is decreased byinserting at least one corneal batten between the layers of the cornealstroma in the limbal region. In this case, the long axis of the cornealbatten is oriented radially to the center of the cornea, i.e., thepupillary axis.

[0022] Alternatively, the radius of curvature of the optic zone isdecreased by inserting at least one corneal batten so as to penetrateseveral layers of the corneal stroma in the limbal region. In this case,the long axis of the corneal batten is oriented tangentially to thecenter of the cornea, i.e., perpendicular to the pupillary axis.

[0023] The radius of curvature of the optic zone is increased byinserting at least one corneal batten so as to penetrate several layersof the corneal stroma in the limbal region. The long axis of the cornealbatten is oriented radially to the center of the cornea, the pupillaryaxis.

[0024] Alternatively, the radius of curvature of the optic zone isincreased by inserting at least one corneal batten between layers of thecorneal stroma in the limbal region. The long axis of the corneal battenis oriented tangentially to the center of the cornea, perpendicular tothe pupillary visual axis.

[0025] These and other objects, features and advantages of the presentinvention will be more readily understood with reference to thefollowing detailed description, read in conjunction with theaccompanying drawing figures.

[0026] All patents referred to or cited herein are incorporated byreference in their entirety to the extent they are not inconsistent withthe explicit teachings of this specification, including: U.S. Pat. No.3,760,807 (Neefe), U.S. Pat. No. 3,776,230 (Neefe), U.S. Pat. No.3,831,604 (Neefe), U.S. Pat. No. 4,381,007 (Doss), U.S. Pat. No.4,799,931 (Lindstrom), U.S. Pat. No. 4,834,748 (McDonald), U.S. Pat. No.4,851,003 (Lindstrom), U.S. Pat. No. 4,907,586 (Bille, et al.), U.S.Pat. No. 4,988,348 (Bille), U.S. Pat. No. 5,002,571 (O'Donnell, Jr., etal.), U.S. Pat. No. 5,063,942 (Kilmer et al.), U.S. Pat. No. 5,108,428(Capecchis, et al.), U.S. Pat. No. 5,201,762 (Huber), U.S. Pat. No.5,269,795 (Arnott), U.S. Pat. No. 5,270,051 (Harris), U.S. Pat. No.5,318,044 (Kilmer et al.), U.S. Pat. No. 5,368,604 (Kilmer et al.), U.S.Pat. No. 5,374,265 (Sand), U.S. Pat. No. 5,395,385 (Kilmer et al.), U.S.Pat. No. 5,632,757 (Arnott), U.S. Pat. No. 5,649,943 (Amoils), U.S. Pat.No. 5,695,509 (El Hage), U.S. Patent No. 5,733,334 (Lee), U.S. Pat. No.5,766,171 (Silvestrini), U.S. Pat. No. 5,776,192 (McDonald), U.S. Pat.No. 5,779,696 (Berry et al.), U.S. Pat. No. 5,788,957 (Harris), U.S.Pat. No. 5,792,161 (de Almeida Cunha), U.S. Pat. No. 5,824,086(Silvestrini), U.S. Pat. No. 5,843,105 (Mathis et al.), U.S. Pat. No.5,855,604 (Lee), U.S. Pat. No. 5,876,439 (Lee), U.S. Pat. No. 5,891,131(Rajan et al), U.S. Pat. No. 5,932,205 (Wang et al.), U.S. Pat. No.5,934,285 (Kritzinger et al.), U.S. Pat. No. 5,944,752 (Silvestrini),and U.S. Pat. No. 6,066,170 (Lee).

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a schematic illustration of a horizontal section of theeye.

[0028]FIG. 2 is a detailed schematic illustration of a horizontalsection of the frontal portion of the eye showing the various layers ofthe cornea.

[0029]FIG. 3 is a perspective view of the corneal batten.

[0030]FIG. 4a is a cross sectional view of the corneal batten having acircular cross section.

[0031]FIG. 4b is a cross sectional view of the corneal batten having ahollow circular cross section.

[0032]FIG. 5a is a cross sectional view of the corneal batten having anelliptical cross section.

[0033]FIG. 5b is a cross sectional view of the corneal batten composedof seven smaller fibers twisted together and bonded with a biologicallyacceptable coating

[0034]FIG. 6 is a schematic illustration of a horizontal section of theeye having a corneal batten implanted radially to the center of vision.

[0035]FIG. 7 is a top view of the eye having a corneal batten implantedradially to the center of the cornea.

[0036]FIG. 8 is a schematic illustration of a horizontal section of theeye having a corneal batten implanted tangent to the optic zone.

[0037]FIG. 9 is a top view of the eye having a corneal batten implantedtangent to the optic zone.

[0038]FIG. 10 is a side view of the frontal portion of the eye havingcorneal batten inserted between the layers of the corneal stroma.

[0039]FIG. 11 is a side view of the frontal portion of the eye havingcorneal batten inserted through multiple layers of the corneal stroma.

DETAILED DISCLOSURE OF THE INVENTION

[0040] The present invention provides an apparatus and method forreshaping the cornea 20 to correct refractive error associated with nearsightedness, far sightedness, and astigmatism.

[0041] In an embodiment of the present invention, as shown in FIGS. 3and 4a, the corneal batten 10 comprises minute fibers made frommaterials with a Young's modulus greater than the Young's modulus of thecorneal stroma 24. One or more of the corneal battens 10 are insertedinto the cornea 20, after selectively distorting the natural cornealshape. Once inserted the stiffness of the corneal batten 10 prevents thecornea 20 from returning to its original curvature.

[0042] In an embodiment, the corneal batten 10 is about 0.1 mm to 16 mmin length, preferably being about 2 mm to 6 mm in length. The crosssectional dimension of the corneal batten 10 is about 0.1 microns to 300microns, preferably having a cross section dimension of about 1.0microns to 25 microns. Materials having a higher Young's modulus of thematerial, enable the corneal batten 10 to have the smaller dimensions.

[0043] In a preferred embodiment, the corneal batten 10 has asubstantially circular cross section. Alternatively, as shown in FIG.5A, the corneal batten's 10 cross section can be elliptical,rectangular, triangular, etc. As well, the corneal batten 10 can possessa hollow cross section, as shown in FIG. 4b.

[0044] In an example, the applied load required to take a 4 mm diametercircular section of the optic zone 22 from ca. 7.7 mm radius ofcurvature to flat (infinite radius of curvature) equates to an appliedpressure that is ca. 1.25 times the intraocular pressure (IOP). As shownin Table 1., graphite corneal battens 10 of circular cross section andof the length and diameters shown require uniformly distributed loadsranging from 0.1 to 51.6 times IOP in order to be deflected fromstraight to a radius of curvature of ca 7.7 mm. It is possible forrelatively small implants to exert force on surrounding tissue equal toor well in excess of the predominant source of load, namely IOP. Ingeneral, the stiffness of a fiber of circular cross section variesinversely with the cube of the fiber length and proportionately with the4^(th) power of the fiber diameter. For any given material modulus,small changes in the fiber length or fiber diameter will permit theconstruction of a corneal batten with the stiffness appropriate for thedesired application. TABLE 1 Multiples of the IOP (18 mm HG assumed)needed to deflect a graphite fiber of circular cross section and of thedimension shown from straight to ca. 7.7 mm radius of curvature (Young'smodulus of 379 × 10⁹ Pascal assumed). Fiber Diameter of fiber in micronsLength (mm) 7.5 15 20 2.0 1.0 16.3  51.6  4.0 0.3 4.0 12.7  6.0 0.1 1.85.7

[0045] To provide −3.00 diopters of power shift to the cornea wouldrequire flattening the schematic cornea from 7.70 mm radius of curvatureon the anterior surface to 8.26 mm radius of curvature. The less thechange in radius, the fewer corneal battens 10 will be needed to bringabout the change.

[0046] In another embodiment, the corneal batten 10 is made from abio-compatible material, acceptable to the ocular environment, having aYoung's modulus greater than that of the corneal stroma 24. Suchbio-compatible material can include, but is not limited to,poly-methylmethacrylate (PMMA), graphite, aluminum oxide, siliconnitride, or silicon carbide.

[0047] In an alternative embodiment, the corneal batten 10 is made froma bio-compatible composite material, acceptable to the ocularenvironment, having a Young's modulus greater than that of the cornealstroma 24. Such bio-compatible composite materials can include, but arenot limited to, PMMA containing graphite fibers or carbon nanotubes,BIOGLASS containing aluminum oxide fibers, graphite fibers or carbonnanotubes. A schematic representation of one possible embodiment of sucha composite is shown in FIG. 5b.

[0048] In a further embodiment, the corneal batten 10 is coated with abio-compatible material, acceptable to the ocular environment. Suchbio-compatible coating material can include, but is not limited to,PMMA, BIOGLASS, or collagen from an appropriate mammalian source. Thecorneal batten 10 can be coated with the bio-compatible material usingtechniques well know in the art, including, dipping in or drawing thecorneal batten through liquified bio-compatible material. Additionally,the bio-compatible material can be polymerized on the corneal batten orvapor deposited. The corneal batten 10 can be coated with solutions ofthe bio-compatible material and then have the solvent evaporated off.

[0049] In another embodiment, the bio-compatible coating materialpromotes cell attachment or contains medications or growth factors whichcan be controllably released.

[0050] In another embodiment, as shown in FIG. 5B, the corneal batten 10is made by spinning or extruded as composites of smaller diameterfibers. Additionally, the corneal batten 10 can be braided from smallerdiameter fibers.

[0051] In a method of use, the corneal batten 10 is implanted into thecorneal stroma 24. The curvature of cornea 20 is controllably altered bythe following: selection of the position of placement of the cornealbattens 10; varying the number of corneal battens 10 implanted; varyingthe dimensions of implanted corneal battens 10; and by flattening orover curving the cornea 20 during placement of the corneal battens 10.The inserted corneal battens 10 will act to alter the stiffness of thesurrounding corneal tissue. This increased stiffness will prevent thenatural forces acting on the cornea 20 from restoring the originalcurvature of the cornea 20 and bring about improved visual acuity.

[0052] The corneal battens 10 are inserted into the corneal stroma 24 bytwo actions. First, an incision can be made in the corneal epithelium 26and Bowman's layer 28 by probing with a sharpened instrument (e.q.scalpel, needle or sharpened cannula) or by pressing the sharpened endof the corneal batten 10 against the corneal epithelium 26 withsufficient force to penetrate the epithelial layer 26 and Bowman's layer28. Next, the corneal stroma 24 may be bluntly dissected with a probeand the batten 10 may be inserted into the resulting pocket, or thecorneal batten 10 itself may be used.

[0053] The placement of the corneal batten 10 and the number used isdetermined by the refractive condition. The initial curvatures anddimensions of the cornea 20 must be ascertained by use of a keratometeror similar instruments. Once these parameters are known, the surgeonswould, by consulting tables developed from experimentation, select thenumber of battens 10 of the desired dimensions and material propertiesneeded to effect the desired alterations. In an example, if the surgeondesired to impart −1.0 diopters of spherical correction to an eye of 7.7mm radius of curvature and 14.1 mm corneal diameter, the recommendednumber of battens 10 of 15 microns diameter and 4.0 mm length would bedetermined from the table and the placement would follow from acceptedpractice. Measurements could be taken again after a portion of thebattens 10 had been placed and corrections could be made, if needed, tothe surgical plan.

[0054] In an embodiment, a computer program is used to determine theindividual dimensions, number required, and the appropriate placement ofthe corneal battens 10. The algorithms used to generate a table would beincorporated into an interactive computer application. The dimensionsand measurements would be entered by hand or taken into the computerdirectly from the measuring equipment and the program would then makerecommendations based on this input. As before, measurements could betaken again after one or more of the battens had been implanted andcorrection could be made, if needed, to the surgical plan.

[0055] In an embodiment, as shown in FIGS. 6, 7 and 10, the radius ofcurvature of the optic zone 22 is decreased by inserting at least onecorneal batten 10 between the layers of the corneal stroma 24 in thelimbal region 30. Where the long axis of the corneal batten 10 isoriented radially to the center of the cornea or pupillary axis 32. Inan embodiment the limbal region 30 of the cornea 20 is flattened with aprobe element to facilitate the insertion of the corneal batten 10between discrete layers of the corneal stroma 22. The probe wouldconsist of a flat surface mounted on a suitable holder. The flat surfaceof the probe would be pressed against that portion of the corneal limbalregion 30 wherein the corneal batten 10 is to be inserted. With thecornea 20 flattened, the surgeon would then insert the corneal batten 10parallel to the flat surface of the probe and a fixed distance from it(e.g. 100 to 400 microns, to be below Bowman's layer 28 and aboveDescemet's membrane 34). With the overall corneal diameter unaltered,the optic zone 22 must take on a smaller radius of curvature tocompensate for the increased radius of curvature of the limbal region 30that was stiffened by the corneal batten 10.

[0056] In an alternative embodiment, the flat surface of the probe couldbe mounted onto the insertion tool for the corneal batten to facilitateuse and insure parallelism.

[0057] In an embodiment, as shown in FIGS. 9 and 11, the radius ofcurvature of the optic zone 22 is decreased by inserting at least onecorneal batten 10 so as to penetrate several layers of the cornealstroma 24 in the limbal region 30. Where the long axis of the cornealbatten 10 is oriented tangentially to the center of the cornea andperpendicular to the pupillary axis 32. In an embodiment the entirelimbal region 30 is rendered more conical in shape with a probe elementduring the insertion of the corneal batten 10 to facilitate the cornealbatten 10 penetrating multiple layers of the corneal stroma 24. Theprobe element would consist of a ring of inner diameter slightly lessthan the diameter of the exterior surface of the cornea where itintersects the plane on which it is desired to pace the corneal batten.The ring would be mounted on a suitable holder. The ring would bepressed against the cornea 20, causing the optic zone 22 to protrudethrough the center of the ring. This protrusion causes the cornea 20 totake on a smaller radius of curvature. The surgeon then inserts one ormore corneal battens 10 in the same plane as the ring. The batten(s) 10are inserted as a chord to the external curvature of the cornea 20 and,thus, would penetrate multiple layers of the stroma 24. With the cornealstroma 24 stiffened by the batten(s) 10, the increased stiffness willprevent the natural forces acting on the cornea 20 from restoring theoriginal curvature.

[0058] In an alternative embodiment, the ring is mounted on theinsertion tools for the corneal battens to facilitate ease of use andinsure co-planarity.

[0059] In an embodiment, as shown in FIGS. 7 and 11, the radius ofcurvature of the optic zone 22 is increased by inserting at least onecorneal batten 10 so as to penetrate several layers of the cornealstroma 24 in the limbal region 30. The long axis of the corneal battenis oriented radially to the center of the cornea or the pupillary axis32. In this embodiment, the optic zone 22 is flattened with a probeelement. The flattening of the optical zone 22 creates a smaller radiusof curvature in the limbal region 30, facilitating the insertion of thecorneal batten 10 through multiple layers of the corneal stroma 24. Theprobe consists of a flat surface mounted on a suitable holder. The flatsurface of the probe is pressed against the optic zone 22. The probe issufficiently small or possesses an opening so as not to obscure thatportion of the corneal limbal region 30 wherein the corneal batten 10 isto be inserted. With the optic zone 22 flattened, the surgeon insertsthe corneal batten 10 at an angle to the flat surface of the probe andso as to be a chord to the exterior curvature of the limbal region 30.With the overall corneal diameter unaltered, the optic zone 22 must takeon a large radius of curvature to compensate for the decreased radius ofcurvature of the limbal region 30 that was stiffened by the cornealbatten 10.

[0060] In an embodiment, the flat surface of the probe is mounted ontothe insertion tool for the corneal batten to facilitate use and insureprecision of placement

[0061] In an alternative embodiment, as shown in FIGS. 8, 9 and 10, theradius of curvature of the optic zone 22 is increased by inserting atleast one corneal batten 10 between layers of the corneal stroma 24 inthe limbal region 30. The long axis of the corneal batten 10 is orientedtangentially to the center of the cornea and perpendicular to thepupillary axis 32. In this embodiment the limbal region 30 of the cornea20 is flattened with a probe element to facilitate the insertion of thecorneal batten 10 between discrete layers of the corneal stroma 24. Theprobe consists of a flat surface mounted on a suitable holder. The flatsurface of the probe is pressed against that portion of the corneallimbal region 30 wherein the corneal batten 10 is to be inserted. Withthe cornea 20 flatted, the surgeon inserts the corneal batten 10parallel to the flat surface of the probe and a fixed distance from theprobe (e.g. 100 to 400 microns, to be below Bowman's Layer 28 and aboveDescemet's membrane 34); tangential to the optic zone 22; andperpendicular to the pupillary axis 32. The corneal stroma 24 isstiffened by the batten 10 and this increased stiffness acts against thenatural forces on the cornea 20 that would restore the originalcurvature. With the overall corneal diameter unaltered, the optic zone22 must also take on a larger radius of curvature to accommodate theincreased radius of curvature to the limbal region 30, tangential to theoptic zone 22, that was stiffened by the corneal batten.

[0062] In an alternative embodiment, the flat surface of the probe ismounted onto the insertion tool for the corneal batten to facilitate useand insure parallelism.

[0063] In a further embodiment a suction cup-form is used to flatten oraccentuate the curvature in the region in which the fiber is beinginserted. In each of the embodiments discussed previously, the probethat was pressed against the cornea 20 by the surgeon is replaced by acup possessing the appropriately shaped inner surface. The cup is placedon the cornea 20 and evacuated. The resulting suction pulls the cornea20 against the inner surface of the cup and the corneal batten(s) 10 areinserted thought appropriately placed ports in the wall to the cup. Thecup maybe mounted onto the insertion tool for the cornea 20 tofacilitate ease of use and precision of placement.

[0064] Following are examples which illustrate procedures for practicingthe invention. These examples should not be construed as limiting.

EXAMPLE 1 Decrease the Radius of Curvature of the Optic Zone

[0065] The radius of curvature of the optic zone 22 can be decreased byflattening the radius of curvature of the limbal region 30 of the cornea20. A portion of the limbal region 30 would be flattened with a probeand a corneal batten 10 would be inserted through the anterior surfacealong a line that extends radially from the edge of the optic zone 22towards the limbus 46. The corneal batten 10 would be inserted at adepth that places it below the Bowman's layer 28 (e.g., 100 microns intothe stroma 24) and parallel to the flattened anterior surface. When theprobe is removed, the limbal region 30, along the line of the cornealbatten 10 will have a higher composite modulus and, thus, will notreturn to as small a radius of curvature. The resulting distortion inthe limbal region 30 must be compensated for by a decrease in the radiusof curvature in the optic zone 22 (along the line of the corneal batten10). As more battens 10 are added around the circle of the optic zone22, the more uniform is the change in curvature inside the optic zone22.

[0066] In a preferred embodiment the corneal 10 is of ca. 7 micronsdiameter and ca. 4 mm length. The corneal batten 10 is made from amaterial possessing a Young's modulus in excess of 100×10⁶ Pascal (1Pascal-1 Newton/square meter). Such a material includes, but not limitedto graphite fiber.

EXAMPLE 2 Flattening the Optic Zone Radius of Curvature

[0067] The radius of curvature of the optic zone 22 can be flattened bydecreasing the radius of curvature of the limbal region 30 of the cornea20. To do this, the optic zone 22 would be flattened with a probe and agraphite fiber of ca. 7 microns diameter and ca. 4 mm length would beinserted through the anterior surface along a line that extends radiallyfrom the edge of the optic zone 22 towards the limbus 46. The fiberwould be inserted at a depth that places it well below the Bowman'slayer 28 and along a line that would lie on the chord for the externalcurvature of the limbal region 30. When the probe is removed, the limbalregion 38 along the line of the fiber will have a higher compositemodulus and, thus, will not return to as large a radius of curvature.This distortion in the limbal region 30 must be compensated for by anincrease in the radius of curvature in the optic zone 22 (along the lineof the fiber). As more fibers are added around the circle of the opticzone 22, the more uniform is the change in curvature inside the opticzone 22.

[0068] It should be understood that the examples and embodimentsdescribed herein are for illustrative purposes only and that variousmodifications or changes in light thereof will be suggested to personsskilled in the art and are included within the spirit and purview ofthis application and the scope of the appended claims.

I claim:
 1. A device for controllably altering the curvature of thecornea comprising a corneal batten, wherein said corneal battencomprises at least one elongated fiber, and where said corneal batten isimplanted into the corneal stroma of an eye.
 2. The corneal battenaccording to claim 1, wherein said corneal batten has a length of about0.1 mm to 16 mm.
 3. The corneal batten according to claim 2, whereinsaid corneal batten has a length of about 2 mm to 6 mm.
 4. The cornealbatten according to claim 1, wherein said corneal batten has a crosssectional dimension of about 0.1 microns to 300 microns.
 5. The cornealbatten according to claim 4, wherein said corneal batten has a crosssectional dimension of about 1 micron to 25 microns.
 6. The cornealbatten according to claim 1, wherein said cross sectional dimension iscircular, elliptical, rectangular or triangular.
 7. The corneal battenaccording to claim 1, wherein said cross sectional is hollow.
 8. Thecorneal batten according to claim 1, wherein said corneal batten is madeof a material having a Young's modulus greater then the Young's modulusof the corneal stroma.
 9. The corneal batten according to claim 1,wherein said corneal batten is made of a bio-compatible material. 10.The corneal batten according to claim 1, wherein said corneal batten iscoated with a bio-compatible material.
 11. The corneal batten accordingto claim 1, wherein said corneal batten is formed by a method selectedfrom the group consisting of extruding, spinning, and braiding saidfibers.
 12. A method for controllably altering the curvature of a corneacomprising the following steps; a) determining the curvature of thecornea; b) selecting at least one corneal batten of suitable dimensionfor correction of the curvature; and c) inserting said corneal batteninto the corneal stroma.
 13. The method for controllably altering thecurvature of the cornea according to claim 12, further comprising thestep of inserting at least one of said corneal battens between thelayers of the corneal stroma in the limbal region.
 14. The method forcontrollably altering the curvature of the cornea according to claim 12,wherein said corneal batten is inserted outside of the optic zone. 15.The method for controllably altering the curvature of the corneaaccording to claim 12, wherein said corneal batten is inserted insidethe optic zone.
 16. The method for controllably altering the curvatureof the cornea according to claim 13, wherein said corneal batten has alongitudinal length which is oriented radially to a center of thecornea, to decrease the radius of curvature of the optic zone.
 17. Themethod for controllably altering the curvature of the cornea accordingto claim 13, wherein said corneal batten has a longitudinal length whichis oriented tangentially to the optic zone and perpendicular to thepupillary axis, to increase the radius of curvature of the optic zone.18. The method for controllably altering the curvature of the corneaaccording to claim 12, further comprising the step of inserting at leastone of said corneal batten through several layers of the corneal stromain the limbal region.
 19. The method for controllably altering thecurvature of the cornea according to claim 18, wherein said cornealbatten has a longitudinal length which is oriented tangential to theoptic zone and perpendicular to the pupillary axis, to decrease theradius of curvature of the optic zone.
 20. The method for controllablyaltering the curvature of the cornea according to claim 18, wherein saidcorneal batten has a longitudinal length which is oriented radially to acenter of the cornea, to increase the radius of curvature of the opticzone.
 21. The method for controllably altering the curvature of thecornea according to claim 12, further comprising the step of alteringthe shape of the limbal region with a probe element prior to insertingsaid corneal batten.
 22. The method for controllably altering thecurvature of the cornea according to claim 21, wherein said probeelement flattens the limbal region of the cornea prior to inserting saidcorneal batten.
 23. The method for controllably altering the curvatureof the cornea according to claim 21, wherein said probe elementincreases the conical shape of the limbal region of the cornea prior toinserting said corneal batten.
 24. A method for effecting refractivecorrection by locally altering the stiffness of the cornea, comprisingthe following steps; a) measuring the curvature of the cornea; b)determining at least one correction location on the cornea; c) selectingat least one corneal batten of suitable dimension; and d) insertion saidcorneal batten into the corneal stroma at said correction location. 25.A computer implemented method of controllably altering the curvature ofthe cornea, comprising the following steps; a) measuring the curvatureof the cornea; b) calculating at least one correction location on thecornea for curvature alternation; c) determining the quantity anddimensions of said corneal battens; and d) insertion said cornealbattens into the corneal stroma at said correction locations.